Diamond, being the hardest substance known, is of great commercial and scientific value. It is inert to chemical corrosion and can withstand compressive forces and radiation. It is an electrical insulator having extremely high electrical resistance but is an excellent thermal conductor, conducting heat better than most other electrical insulators. Diamond is structurally similar to silicon but is a wide-band-gap semiconductor (5 eV) and so is transparent to UV-visible light and to much of the infrared spectrum. It has an unusually high breakdown voltage and low dielectric constant. These properties, coupled with recent advances, have led to speculation that diamond might find widespread application in high speed electronic devices and devices designed to be operated at high temperature. If it can be doped successfully diamond could become an important semiconductor material on which new or replacement device applications may be based. While silicon chips can withstand temperatures up to 300.degree. C., it is estimated that diamond devices may be able to withstand considerably higher temperatures. Diamond film already find applications as hard protective coatings.
Because of these useful properties, synthetic diamond has great potential in research and commercial applications. Synthetic diamonds are now produced by two known methods: a high pressure process in which carbonaceous material is compressed into diamond using high pressure anvils; and the more recent technique of chemical vapour deposition (CVD) in which diamond films are deposited on an appropriate substrate by decomposing a carbon containing gaseous precursor.
Of recent particular scientific interest are a class of carbon structures known as Buckminster fullerenes which are formed by an integral number of carbon atoms which combine to form a closed, roughly spherical structure. Two prominent fullerenes are C.sub.60 and C.sub.70, which are spherical structures comprising 60 and 70 carbon atoms, respectively. The successful transformation of C.sub.60 and C.sub.70 into diamond at high pressure has been disclosed by Manuel Nunez Regueiro, Pierre Monceau, Jean-Louis Hodeau, Nature, 355, 237-239 (1992) and Manuel Nunez Regueiro, L. Abello, G. Lucazeau, J. L. Hodeau, Phys. Rev. B, 46, 9903-9905 (1992). The transition of C.sub.60 to diamond has also been studied by Hisako Hirai, Ken-ichi Kondo and Takeshi Ohwada, Carbon, 31, 1095-1098 (1993). It is also known that C.sub.70 can accelerate the nucleation of diamond thin film formation on metal surfaces using CVD as disclosed by R. J. Meilunas, R. P. H. Chang, S. Liu, M. M. Kappes, Appl. Phys. Lett., 59, 3461-3463 (1991), and R. J. Meilunas, R. P. H. Chang, S. Liu, M. M. Kappes, Nature, 354, 271 (1991).
A high growth rate of diamond film using fullerene precursors in an argon microwave plasma with or without hydrogen has been reported by D. M. Gruen, S. Liu, A. R. Krauss and X. Pan, J. Appl. Phys., 75, 1758-1763 (1994), and D. M. Gruen, S. Liu, A. R. Krauss, J. Luo and X. Pan, Appl. Phys. Lett., 64, 1502-1504 (1994).
Recently, dispersed diamond particles with diameters in the range of 20-150.ANG.have been observed in fullerene-rich soot as disclosed by Vladimir Kuznetsov, A. L. Chuvilin, E. M. Moroz, V. N. Kolomiichuk, Sh. K. Shaikhutdinov, Yu. V. Butenko, Carbon, 32, 873-882 (1994), and Vladimir L. Kuznetsov, Andrey L. Chuvilin, Yuri V. Butenko, Igor Yu. Malkov, Vladimir M. Titov, Chem. Phys. Lett., 222, 343-348 (1994). It would be very advantageous and of potentially significant commercial value to be able to grow diamond particles with much larger particle sizes.